System and method of assuring drop out of a solenoid valve

ABSTRACT

A method of assuring drop out of a valve assembly comprising detecting a level of a signal from the controller; diverting the signal to a solenoid coil of the valve assembly when the level of the signal is above a predetermined value; and diverting the signal to a load when the level of the signal is below the predetermined value. The level detector may divert the signal away from the coil when the level of the signal is below the predetermined value, thereby ensuring that the coil is fully de-energized in response to the level of the signal being below the predetermined value, while allowing current to flow through the valve assembly, thereby allowing the controller to monitor the integrity of the wiring between the controller and the valve assembly.

CROSS REFERENCE TO RELATED APPLICATIONS

None.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO APPENDIX

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The inventions disclosed and taught herein relate generally tosolenoids; and more specifically relate to solenoids used in processcontrol valves.

2. Description of the Related Art

U.S. Pat. No. 3,577,040 discloses an “electronic circuit for actuating asolenoid load from an AC power source in a two-step sequence wherein ahigh DC voltage is initially applied to “pull-in” the solenoid armatureand a lower voltage maintains the armature in a “hold” condition.Silicon-controlled rectifiers (SCR's) provide an electronic switchingand rectification of the voltage for operating power. The circuit iscontrolled by an electrical signal which conditions the SCR's to provideoperating voltage during alternate half cycles of the power source and atime delay circuit allows conduction of the “pull-in” SCR for only a fewcycles of the power source.”

U.S. Pat. No. 3,660,730 discloses a “circuit for initially applying anunusually large drive voltage to a solenoid coil and for subsequentlyreducing the applied voltage during the travel of the solenoid plunger.The solenoid coil is serially connected to a first transistor circuitoperating as an on-off switch and also is serially connected to a secondtransistor circuit operating to variably control the voltage applied tothe solenoid. A capacitor-charge timing circuit controls the variabletransistor and thereby gradually reduces the voltage applied to thesolenoid.”

U.S. Pat. No. 7,073,524 discloses a “fail-safe apparatus for controllingfluid flow through a series arrangement of first and secondsolenoid-controlled valves is provided. The fail-safe apparatus includesfail-safe circuitry for controlling the operation of the first andsecond solenoid-controlled valves between unactuated and actuatedstates. Based on a given duty cycle, the fail-safe circuitry selects,actuates, deactuates, and/or maintains in the actuated or unactuatedstate one or both of the first and second solenoid-controlled valves. Tofacilitate such control, the fail-safe circuitry may include a switchoperable to couple an input voltage across the first solenoid-controlledvalve to cause a first current to flow therein. The fail-safe circuitrymay also include an energy-transfer device coupled between the first andsecond solenoid-controlled valves. Depending of the duty cycle, theenergy-transfer device is operable to store a potential therein and/oruse the stored potential to assist in controlling the first and secondsolenoid-controlled valves.”

U.S. Patent Application Publication No. 20110094589 discloses a “methodof solenoid valve control includes measuring voltage across the solenoidvalve and current through the solenoid valve, and using the results toaid in controlling the solenoid valve. For instance, one or both of themeasured values may be used to determine when actual engagement of thesolenoid valve occurs. An initial lower voltage and lower current can beused, and then as conditions change, the changes in condition can beaccounted for by increasing voltage and current to maintain the desiredresponse time of the solenoid valve. By measuring and controllingvoltage and current less of a margin can be used, both in settingvoltage/current levels and in selecting the time over which a pullvoltage/current is utilized. This reduces the wasted energy in thesystem, as well as reducing the temperature rise in the solenoid valve.”

Patent No. WO2011053392A1 discloses a “method of controlling a solenoidvalve (12) includes the steps of: initiating engagement of the solenoidvalve by applying to the solenoid valve either a pull-in voltage or apull-in current; during the applying, monitoring at least one of averagevoltage across the solenoid valve (40) or current through the solenoidvalve (50); from the monitoring, determining completion of engagement ofthe solenoid valve; and after the determining, reducing either thepull-in voltage to a hold voltage, or the pull-in current to a holdcurrent.”

The inventions disclosed and taught herein are directed to an improvedsystem and method for assuring drop out of a solenoid valve.

BRIEF SUMMARY OF THE INVENTION

A method of assuring drop out of a valve assembly comprising detecting alevel of a signal from the controller; diverting at least a portion ofthe signal from the controller to a solenoid coil of the valve when thelevel of the signal is above a predetermined value; and diverting atleast a portion of the signal from the controller to a load when thelevel of the signal is below the predetermined value. The predeterminedvalue may be about 10 volts or between 5 and 10 volts. The leveldetector may divert all or a portion of the signal from the controlleraway from the load when the level of the signal is above thepredetermined value, thereby minimizing power waste when the controlleractuates the valve assembly. The level detector may divert all or aportion of the signal from the controller away from the coil when thelevel of the signal is below the predetermined value, thereby ensuringthat the coil is fully de-energized in response to the level of thesignal from the controller being below the predetermined value, whileallowing a current of the signal to flow through the valve assembly,thereby allowing the controller to monitor a wiring integrity betweenthe controller and the valve assembly.

A system for assuring drop out of a valve assembly comprising a processcontrol valve; a solenoid coil configured to selectively actuate thecontrol valve upon receipt of an actuation signal from a controller; aload to sink a wiring integrity signal from the controller; and a leveldetector that monitors a control signal from the controller anddetermines whether the control signal from the controller constitutesthe actuation signal or the wiring integrity signal. The level detectormay be configured to divert the actuation signal to the solenoid coiland/or away from the load. The level detector may be configured todivert the wiring integrity signal to the load and/or away from thecoil.

A system for assuring drop out of a valve assembly comprising acontroller configured the control a process using the valve assembly andwiring between the controller and the valve assembly, the controllerconfigured to generate a control signal; and the valve assemblycomprising a process control valve configured to influence the processaccording to the control signal; a level detector configured to monitorthe signal from the controller and determine whether the signal from thecontroller is above a predetermined value a solenoid coil configured toselectively actuate the control valve upon receipt of the signal fromthe controller above the predetermined value; and a load to sink thesignal from the controller below the predetermined value. The leveldetector may be configured to divert the signal to the solenoid coiland/or away from the load if the signal from the controller is above thepredetermined value. The level detector may be further configured todivert the signal to the load and/or away from the coil if the signalfrom the controller is below the predetermined value.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates a simplified block diagram of a particular embodimentof a system for process control utilizing certain aspects of the presentinventions;

FIG. 2 illustrates exemplary control signal levels that may be used withthe system of FIG. 1;

FIG. 3 illustrates a simplified block diagram of a solenoid valveutilizing certain aspects of the present inventions;

FIG. 4 illustrates a schematic of a particular embodiment of a solenoidmodule for use with the solenoid valve of FIG. 3 and/or the processcontrol system of FIG. 1 utilizing certain aspects of the presentinventions;

FIG. 5 is the schematic diagram of FIG. 4 showing current flowassociated with a high power control signal utilizing certain aspects ofthe present inventions;

FIG. 6 is the schematic diagram of FIG. 4 showing current flowassociated with a low power control signal utilizing certain aspects ofthe present inventions; and

FIG. 7 illustrates a schematic of a microprocessor embodiment ofportions of a solenoid module for use with the solenoid valve of FIG. 3and/or the process control system of FIG. 1 utilizing certain aspects ofthe present inventions;

DETAILED DESCRIPTION OF THE INVENTION

The Figures described above and the written description of specificstructures and functions below are not presented to limit the scope ofwhat Applicants have invented or the scope of the appended claims.Rather, the Figures and written description are provided to teach anyperson skilled in the art to make and use the inventions for whichpatent protection is sought. Those skilled in the art will appreciatethat not all features of a commercial embodiment of the inventions aredescribed or shown for the sake of clarity and understanding. Persons ofskill in this art will also appreciate that the development of an actualcommercial embodiment incorporating aspects of the present inventionswill require numerous implementation-specific decisions to achieve thedeveloper's ultimate goal for the commercial embodiment. Suchimplementation-specific decisions may include, and likely are notlimited to, compliance with system-related, business-related,government-related and other constraints, which may vary by specificimplementation, location and from time to time. While a developer'sefforts might be complex and time-consuming in an absolute sense, suchefforts would be, nevertheless, a routine undertaking for those of skillin this art having benefit of this disclosure. It must be understoodthat the inventions disclosed and taught herein are susceptible tonumerous and various modifications and alternative forms. Lastly, theuse of a singular term, such as, but not limited to, “a,” is notintended as limiting of the number of items. Also, the use of relationalterms, such as, but not limited to, “top,” “bottom,” “left,” “right,”“upper,” “lower,” “down,” “up,” “side,” and the like are used in thewritten description for clarity in specific reference to the Figures andare not intended to limit the scope of the invention or the appendedclaims.

Applicants have created a method of assuring drop out of a valveassembly comprising detecting a level of a signal from the controller;diverting at least a portion of the signal from the controller to asolenoid coil of the valve when the level of the signal is above apredetermined value; and diverting at least a portion of the signal fromthe controller to a load when the level of the signal is below thepredetermined value. The predetermined value may be about 10 volts orbetween 5 and 10 volts. The level detector may divert all or a portionof the signal from the controller away from the load when the level ofthe signal is above the predetermined value, thereby minimizing powerwaste when the controller actuates the valve assembly. The leveldetector may divert all or a portion of the signal from the controlleraway from the coil when the level of the signal is below thepredetermined value, thereby ensuring that the coil is fullyde-energized in response to the level of the signal from the controllerbeing below the predetermined value, while allowing a current of thesignal to flow through the valve assembly, thereby allowing thecontroller to monitor a wiring integrity between the controller and thevalve assembly.

Applicants have also created a system for assuring drop out of a valveassembly comprising a process control valve; a solenoid coil configuredto selectively actuate the control valve upon receipt of an actuationsignal from a controller; a load to sink a wiring integrity signal fromthe controller; and a level detector that monitors a control signal fromthe controller and determines whether the control signal from thecontroller constitutes the actuation signal or the wiring integritysignal. The level detector may be configured to divert the actuationsignal to the solenoid coil and/or away from the load. The leveldetector may be configured to divert the wiring integrity signal to theload and/or away from the coil.

Applicants have also created a system for assuring drop out of a valveassembly comprising a controller configured the control a process usingthe valve assembly and wiring between the controller and the valveassembly, the controller configured to generate a control signal; andthe valve assembly comprising a process control valve configured toinfluence the process according to the control signal; a level detectorconfigured to monitor the signal from the controller and determinewhether the signal from the controller is above a predetermined value asolenoid coil configured to selectively actuate the control valve uponreceipt of the signal from the controller above the predetermined value;and a load to sink the signal from the controller below thepredetermined value. The level detector may be configured to divert thesignal to the solenoid coil and/or away from the load if the signal fromthe controller is above the predetermined value. The level detector maybe further configured to divert the signal to the load and/or away fromthe coil if the signal from the controller is below the predeterminedvalue.

FIG. 1 is an illustration of a valve assembly 10 according to certainaspects of the present inventions. The valve assembly 10 preferablycontrols flow of a process control media, such as a liquid or gas,through a process control line 12, as directed by a process controlcontroller 14. More specifically, the controller 14 is preferablyelectrically coupled to the valve assembly 10, in order to allow and/orprevent flow of the media through the process control line 12 bycommanding the valve assembly 10 to open and/or close. The controller 14controls the valve assembly 10 by selectively electrically energizing asolenoid module 16 the physically opens and/or closes a process controlvalve 18, which in turn allows and/or prevents flow of the media throughthe process control line 12.

Some controllers 14 do not completely drop the power, voltage and/orcurrent, that they supply to the valve assembly 10, when the controller14 commands the valve assembly 10 to return to its normal state. Morespecifically, the valve assembly 10 may function as a normally openvalve, in which case it allows the flow of the media through the processcontrol line 12 in the absence of energizing power from the controller14, or a normally closed valve, in which case it prevents the flow ofthe media through the process control line 12 in the absence ofenergizing power from the controller 14. To close a normally open valveassembly 10, or open a normally closed valve assembly 10, the controller14 energizes the solenoid module 16, which in turn physically shifts thecontrol valve 18. In order to return to the valve assembly's 10 normalposition, open or closed, the controller 14 energizes the solenoidmodule 16, or stops providing full power, voltage and/or current to thevalve assembly 10.

Some controllers 14 completely drop the power, voltage and/or currentthat they supply to the valve assembly 10 to zero, when they command thevalve assembly 10 to return to the normal state. However, somecontrollers 14 merely drop the power, voltage and/or current that theysupply to the valve assembly 10 to a less than full power value, whenthey command the valve assembly 10 to return to the normal state. Morespecifically, some controllers 14 do not drop the power, voltage and/orcurrent that they supply to the valve assembly 10 to zero, when theycommand the valve assembly 10 to return to the normal state. Rather,some controllers 14 still supply some power, voltage and/or current tothe valve assembly 10 to zero, when they command the valve assembly 10to return to the normal state.

For example, referring also to FIG. 2, there are systems withcontrollers 14 that allow a small supervisory current to flow in thenormal or powered down state. More specifically, it can be seen in FIG.2 that the controller 14 supplies about twelve volts, with an associatedcurrent, to the valve assembly 10 in order to command the valve assembly10 to actuate, that is to say open, in the case of a normally closedvalve assembly 10, or close, in the case of a normally open valveassembly 10. As mentioned, some controllers 14 would supply zero voltageand current, in order to command the valve assembly 10 to return to itsnormal state.

As also mentioned, some controllers 14 would supply a lesser voltage andcurrent, such as the two volts shown at an associated, in order tocommand the valve assembly 10 to return to its normal state. This normalstate, or residual, power, voltage, or current may be used to allow thecontroller 14 to confirm that the wiring and connections in the systemare intact and functional. Failure to pass power, voltage, or current inthis loop will result in some form of system alarm that notifiesoperators that there is a potential problem with the operation of thesystem, wiring, and/or connections controlling the valve assembly 10.

Referring also to FIG. 3, in order to accomplish this functionality, asolenoid module 16 utilizing certain aspects of the present inventionmay be utilized. The solenoid module 16 may have a level detector 20that monitors and directs the power, voltage, and/or current from thecontroller 14. For example, the level detector 20 may direct high power,voltage, and/or current from the controller 14 to a solenoid coil 22,which actuates the control valve 18. The level detector 20 may alsodirect low power, voltage, and/or current from the controller 14 to aload 24, which allows the controller 14 to verify the wiring between thecontroller 14 and the solenoid module 16 while ensuring that thesolenoid coil 22 is sufficiently de-energized to reliably return thevalve assembly 10 to its normal state.

FIG. 4 illustrates a specific embodiment of the solenoid module 16utilizing certain aspects of the present invention. As shown, the leveldetector 20 may comprise a circuit including various resistors, diodes,and transistors that shift current flow depending on the level of thepower, voltage, and/or current from the controller 14.

Referring also to FIG. 5, a high power, voltage, and/or current signalfrom the controller 14 will now be explained. The high power signal fromthe controller 14 flows though a first diode 26. A majority of the highpower signal from the controller 14 then flows down through the firstbi-polar junction transistor (BJT) 28. Some of that signal is divertedthrough the base of the first BJT reverse biasing a second diode 30,such as a zener diode. The remainder of the signal flowing through thefirst BJT 28 then flows through the solenoid coil 22, thereby actuatingthe valve assembly 10. In the example shown, the second diode is a zenerdiode rated at 9.1 volts. Thus, the signal from the controller 14 mustbe about ten volts, or greater, in order to energize the solenoid coil22. More specifically, there is about a one volt drop across the firstdiode 26 and first BJT 28. The second diode 30 holds the base of thefirst BJT 28 at about 9.1 volts. Thus, for there to be current flowthrough the first BJT 28 to the solenoid coil 22, the signal from thecontroller 14 must be about ten volts, or greater. If the signal fromthe controller 14 is less than about 10 volts, in the specificembodiment shown, the voltage drops incurred at the first diode 26 andthe first BJT 28 will reduce the voltage of the signal from thecontroller 14, as seen at the base of the first BJT 28, to less than thereverse break down voltage of the second diode 30, thereby blockingcurrent flow through the first BJT 28 to the solenoid coil 22.

Of course, the exact selection of the first and second diodes 26, 30 andfirst BJT 28 will control the minimum value that the high power signalcan be, in order to reliably energize the solenoid coil 22, therebyactuating the valve assembly 10. For example, selecting the first diode26 and first BJT 28 to have low voltage drops, or even omitting thefirst diode 26, will permit the solenoid coil 22 to be energized withsignals from the controller 14 closer to the rating of the second diode30. Likewise, selecting a zener diode with a lower reverse breakdownvoltage for the second diode will also lower the minimum value that thehigh power signal can be, in order to reliably energize the solenoidcoil 22, thereby actuating the valve assembly 10.

Where the signal from the controller 14 is less than about 10 volts,referring also the FIG. 6, the voltage drops across the first and seconddiodes 26, 30 and first BJT 28 will prevent current flow through thefirst BJT 28 and the solenoid coil. But, as mentioned above, a wiringintegrity monitoring signal from the controller 14 through the valveassembly 10 may be desirable to monitor and ensure the integrity of thewiring between the controller 14 and the valve assembly 10. Thus, thislower power signal from the controller 14 is diverted to the load 24,such as a load resistor. In one specific embodiment, a gate of a fieldeffect transistor (FET) 32, such as a BSS138 enhancement mode metaloxide semiconductor field effect transistor (MOSFET) available fromFairchild Semiconductor, is pushed above the threshold voltage by asecond BJT 34, thereby biasing the FET 32 and drawing the low powersignal from the controller 14 through the load resistor 24.

The current drawn through the load resistor 24 and the FET 32 is limitedby the interaction between the second BJT 34 and a control resistor 36.For example, the higher the currently flowing through the controlresistor 36, the higher the voltage across the control resistor 36. Ahigher voltage across the control resistor 36 biases the second BJT 34to a greater degree, thereby drawing more current through the second BJT34, which in turn draws more current through a FET biasing resistor 38.As more current flows through the FET biasing resistor 38, the voltageat the gate of the FET 32 drops, thereby shutting off the FET 32 andstopping current flow through the load resistor 24.

This is also how the present invention prevents wasteful current flowthrough the load resistor 24, when the controller 14 sends a high powersignal to the valve assembly 10, meant to actuate the valve assembly.More specifically, as can be seen, current flowing through the solenoidcoil 22 also flows though the control resistor 36, thereby raising thebase voltage of the second BJT 34 and biasing the second BJT 34 to agreater degree. This draws more current through the second BJT 34, whichin turn draws more current through a FET biasing resistor 38, therebydropping the voltage at the gate of the FET 32 drops, shutting off theFET 32, and stopping current flow through the load resistor 24.

In this manner, the present invention allows the controller 14 to send alow power signal through the wiring to the valve assembly 10, therebymonitoring the integrity of the wiring between the controller 14 and thevalve assembly 10. At the same time, the present invention still ensuresthat the solenoid coil will be de-energized, thereby ensuring that thevalve assembly will reliably return to the normal state, in the face ofthis low power signal wiring integrity monitoring signal. On the otherhand, the present invention allows the controller 14 to send a highpower signal through the wiring to the valve assembly 10, therebyactuating the valve assembly 10 without wasteful current through theload resistor 24. Thus, it can be seen that the solenoid module 16 ofthe present invention actually and efficiently diverts the high power,actuation signal from the controller 14 to the solenoid coil 22 andactually and efficiently diverts the low power, wiring integritymonitoring signal from the controller 14 to the load resistor 24.

Other and further embodiments utilizing one or more aspects of theinventions described above can be devised without departing from thespirit of Applicant's invention. For example, the various methods andembodiments of the present invention can be included in combination witheach other to produce variations of the disclosed methods andembodiments. Additionally, other circuit designs may be used.Furthermore, other voltage levels, such as six volts or eight volts, orvoltage ranges, such as between five and ten volts may be used as thepredetermined voltage at which the system switches between the actuatedstate and the normal state.

For example, the ten volt predetermined voltage value is expected towork well with a solenoid coil 22 that is rated for twenty-four voltsdirect current (DC). However, the predetermined voltage value, at whichthe level detector 20 switches, may be changed according to a nominalcoil voltage, such that this switching point will be some fraction ofthe nominal coil voltage. The switching functionality of the leveldetector 20 may be provided by, or with the assistance of, amicroprocessor and supporting circuitry.

For example, referring also to FIG. 7, a voltage comparator may bemonitored by the microprocessor which in turn causes one or more loadresistors 24 to be connected across the input when the input is at orbelow a 10.5 volt predetermined switching voltage or value. When theinput is at or above the 10.5 volt predetermined switching value, themicroprocessor may divert the input signal to the solenoid coil 22 (seeFIG. 3) and/or trigger logic to charge the capacitors and open the valve18 (see FIG. 3).

Configurations such as this may be configured to provide somehysteresis, and/or range to the predetermined switching voltage value,such that the input is diverted to the coil 22 (see FIG. 3) when theinput rises above 10.5 volt and the input is diverted to the loadresistors 24 when the input falls below about eight volts. This wouldprevent inadvertent cycling of the solenoid coil 22 (see FIG. 3), andthus the control valve 18 (see FIG. 3), due to fluctuations in the inputsignal.

The order of steps can occur in a variety of sequences unless otherwisespecifically limited. The various steps described herein can be combinedwith other steps, interlineated with the stated steps, and/or split intomultiple steps. Similarly, elements have been described functionally andcan be embodied as separate components or can be combined intocomponents having multiple functions. Discussion of singular elementscan include plural elements and vice-versa.

The inventions have been described in the context of preferred and otherembodiments and not every embodiment of the invention has beendescribed. Obvious modifications and alterations to the describedembodiments are available to those of ordinary skill in the art. Thedisclosed and undisclosed embodiments are not intended to limit orrestrict the scope or applicability of the invention conceived of by theApplicants, but rather, in conformity with the patent laws, Applicantsintend to fully protect all such modifications and improvements thatcome within the scope or range of equivalent of the following claims.

What is claimed is:
 1. A method of assuring drop out of a valveassembly, the method comprising the steps of: receiving, at the valveassembly, a signal from a controller; detecting a level of the signalfrom the controller; diverting, in response to the level of the signalfrom the controller being above a predetermined value, at least aportion of the signal from the controller to a solenoid coil of thevalve assembly, the level of the signal diverted to the solenoid coilbeing above the predetermined value; and diverting, in response to thelevel of the signal from the controller being below the predeterminedvalue, at least a portion of the signal from the controller to a load,the level of the signal diverted to the load being below thepredetermined value, wherein a level detector determines whether thesignal from the controller is above the predetermined value before thesignal is received by the solenoid coil or the load.
 2. The method ofclaim 1, wherein the predetermined value is about 10 volts.
 3. Themethod of claim 1, wherein the predetermined value is between 5 and 10volts.
 4. The method of claim 1, further including diverting at least aportion of the signal from the controller away from the load when thelevel of the signal is above the predetermined value.
 5. The method ofclaim 1, further including diverting all of the signal from thecontroller away from the load when the level of the signal is above thepredetermined value.
 6. The method of claim 1, further includingdiverting the signal from the controller away from the load when thelevel of the signal is above the predetermined value, thereby minimizingpower waste when the controller actuates the valve assembly.
 7. Themethod of claim 1, further including diverting at least a portion of thesignal from the controller away from the coil when the level of thesignal is below the predetermined value.
 8. The method of claim 1,further including diverting all of the signal from the controller awayfrom the coil when the level of the signal is below the predeterminedvalue.
 9. The method of claim 1, further including diverting all of thesignal from the controller away from the coil when the level of thesignal is below the predetermined value, thereby ensuring that the coilis fully de-energized in response to the level of the signal from thecontroller being below the predetermined value, and allowing a currentof the signal to flow through the valve assembly, thereby allowing thecontroller to monitor a wiring integrity between the controller and thevalve assembly.
 10. The method of claim 1, further including sending thesignal from the controller to the valve assembly at a high level abovethe predetermined value in order to actuate the valve assembly andsending the signal from the controller to the valve assembly at a lowlevel below the predetermined value in order to return the valveassembly to a normal state.
 11. A system for assuring drop out of avalve assembly comprising: a process control valve; a solenoid coilconfigured to selectively actuate the control valve upon receipt of anactuation signal from a controller; a load to sink a wiring integritysignal from the controller; and a level detector that monitors a controlsignal from the controller and determines whether the control signalfrom the controller constitutes the actuation signal or the wiringintegrity signal before the control signal is received by the solenoidcoil or the load.
 12. The system of claim 11, wherein the level detectoris further configured to divert the actuation signal to the solenoidcoil.
 13. The system of claim 11, wherein the level detector is furtherconfigured to divert the actuation signal away from the load.
 14. Thesystem of claim 11, wherein the level detector is further configured todivert the wiring integrity signal to the load.
 15. The system of claim11, wherein the level detector is further configured to divert thewiring integrity signal away from the coil.
 16. The system of claim 11,wherein the level detector is further configured to divert the signal tothe solenoid coil if the signal from the controller is above thepredetermined value.
 17. The system of claim 11, wherein the leveldetector is further configured to divert the signal away from the loadif the signal from the controller is above the predetermined value. 18.The system of claim 11, wherein the level detector is further configuredto divert the signal to the load if the signal from the controller isbelow the predetermined value.
 19. The system of claim 11, wherein thelevel detector is further configured to divert the signal away from thecoil if the signal from the controller is below the predetermined value.20. A system for assuring drop out of a valve assembly comprising: acontroller configured—to—control a process using the valve assembly andwiring between the controller and the valve assembly, the controllerconfigured to generate a control signal; and the valve assemblycomprising— a process control valve configured to influence the processaccording to the control signal; a level detector configured to monitorthe signal from the controller and determine whether the signal from thecontroller is above a predetermined value; a solenoid coil configured toselectively actuate the control valve upon receipt of the signal fromthe controller above the predetermined value; and a load to sink thesignal from the controller below the predetermined value; wherein thelevel detector determines whether the signal from the controller isabove the predetermined value before the control signal is received bythe solenoid coil or by the load.